Novel solid forms of epalrestat

ABSTRACT

The invention relates to novel crystalline salts of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid and a novel betaine cocrystal of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid. The preparation and characterization of the novel crystalline salts and cocrystal according to various embodiments of the invention is described. The invention also relates to pharmaceutical compositions containing the novel crystalline salts and cocrystal and the therapeutic use of the novel crystalline salts and cocrystal to treat and/or prevent various conditions, including treating and/or preventing diabetic complications, inhibiting aldose reductase, and affording cardioprotection in patients who may be non-diabetic.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of International ApplicationNo. PCT/US2009/047060, filed on Jul. 24, 2009, which published inEnglish as WO 2009/152347, and claims priority under 35 U.S.C. §119 toU.S. Provisional Application 61/083,611, filed Jul. 25, 2008, both ofwhich are incorporated herein by reference. This application is also acontinuation-in-part of International Application No. PCT/US2009/051693,filed on Jul. 24, 2009, which published in English as WO 2010/011926,and claims priority under 35 U.S.C. §119 to U.S. Provisional Application61/083,619, filed Jul. 25, 2008, both of which are incorporated hereinby reference.

TECHNICAL FIELD

One aspect of the invention described herein relates to novelcrystalline salts of5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineaceticacid, processes for making those novel crystalline salts, pharmaceuticalcompositions comprising those novel crystalline salts, and methods oftreating and/or preventing various conditions by administering thosenovel crystalline salts.

A further aspect of the invention described herein relates to a novelbetaine cocrystal of5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineaceticacid, processes for making the novel betaine cocrystal, pharmaceuticalcompositions comprising the novel betaine cocrystal, and methods oftreating and/or preventing various conditions by administering the novelbetaine cocrystal.

BACKGROUND

The compound5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineaceticacid (shown below), referred to by its common name “epalrestat,” is aknown active pharmaceutical ingredient (“API”) having beneficialtherapeutic activity, for example as an aldose reductase inhibitor:

The preparation and pharmacologic activity of epalrestat is described inU.S. Pat. No. 4,831,045. Epalrestat is useful in treating and/orpreventing various conditions such as, for example, complications ofdiabetes, as well as affording cardioprotection in non-diabeticpatients. For example, epalrestat has a positive indication for thetreatment and/or prevention of diabetic neuropathy, and is useful forthe treatment and/or prevention of various other diabetic complicationsincluding, for example, diabetic retinopathy, diabetic nephropathy,diabetic cardiomyopathy, diabetic gastroparesis, diabeticmicroangiopathy, and diabetic macroangiopathy in mammals. Epalrestat isalso useful in affording cardioprotection to subjects who may not besuffering from diabetes, and as a neuroprotectant or treatment forneurological or neurodegenerative disorders. Therapeutic activity ofepalrestat in various conditions has been demonstrated in the clinicalliterature, including but not limited to Machii H. et al., Gendai Iryo,1996; 28:1273; Miyamoto S. et al., Gendai Iryo, 1986; 18 (Extra IssueIII):82; Goto Y. et al., Journal of Clinical and Experimental Medicine,1990; 152:405; Nakano K. et al., Journal of Clinical and ExperimentalMedicine, 1990; 152:137; Okamoto H. et al., Internal Medicine, 2003;42:655-664; Hamada Y. et al., Diabetes Care 2000; 23:1539-44.; Goto Y.et al., Diabet Med 1993; 10(suppl 2):S39-43; Goto Y. et al., BiomedPharmacother 1995; 49:269-77; Uchida K. et al., Clin Ther 1995;17:460-6; Hotta N. et al., J Diabetes Complications 1996; 10:168-72;Hotta N. et al., Diabetes Care 2006; 29:1538-44; Matsuoka K. et al.,Diabetes Res Clin Pract 2007; 77(suppl 1):S263-8; Nakayama M. et al.,Diabetes Care 2001; 24:1093-8; Baba M., Journal of the PeripheralNervous System 2003; 8:170; Yasuda H. et al., Diabetes Care 2000;23:705; Ikeda T et al., Diabetes Research and Clinical Practice 1999;43:193-198; Katayama M. et al., Electroencephalography and ClinicalNeurophysiology/Electromyography and Motor Control 1995; 97:81; andMisawa S. et al., Neurology 2006; 66:1545-9.

Although therapeutic efficacy is a primary concern for a therapeuticagent, such as epalrestat, the salt and solid state form (e.g.crystalline or amorphous forms) of a drug candidate can be important toits pharmacological properties and to its development as a viable API.For example, each salt or each crystalline form of a drug candidate canhave different solid state (physical and chemical) properties. Thedifferences in physical properties exhibited by a particular solid formof an API, such as a cocrystal, salt, or polymorph of the originalcompound, can affect pharmaceutical parameters of the API. For example,storage stability, compressibility and density, all of which can beimportant in formulation and product manufacturing, and solubility anddissolution rates, which may be important factors in determiningbioavailability, may be affected. Because these physical properties areoften influenced by the solid state form of the API, they cansignificantly impact a number of factors, including the selection of acompound as an API, the ultimate pharmaceutical dosage form, theoptimization of manufacturing processes, and absorption in the body.Moreover, finding the most adequate form for further drug developmentcan reduce the time and the cost of that development.

Obtaining pure crystalline forms, then, is extremely useful in drugdevelopment. It may permit better characterization of the drugcandidate's chemical and physical properties. For example, crystallineforms often have better chemical and physical properties than amorphousforms. As a further example, a crystalline form may possess morefavorable pharmacology than an amorphous form, or may be easier toprocess. It may also have better storage stability.

One such physical property which can affect processability is theflowability of the solid, before and after milling. Flowability affectsthe ease with which the material is handled during processing into apharmaceutical composition. When particles of the powdered compound donot flow past each other easily, a formulation specialist must take thatfact into account in developing a tablet or capsule formulation, whichmay necessitate the use of additional components such as glidants,including colloidal silicon dioxide, talc, starch, or tribasic calciumphosphate.

Another solid state property of a pharmaceutical compound that may beimportant is its dissolution rate in aqueous fluid. The rate ofdissolution of an active ingredient in a patient's stomach fluid mayhave therapeutic consequences since it can impact the rate at which anorally administered active ingredient may reach the patient'sbloodstream.

Another solid state property of a pharmaceutical compound that may beimportant is its thermal behavior, including its melting point. Themelting point of the solid form of a drug is optionally high enough toavoid melting or plastic deformation during standard processingoperations, as well as concretion of the drug by plastic deformation onstorage (See, e.g., Gould, P. L. Int. J. Pharmaceutics 1986 33 201-217).It may be desirable in some cases for a solid form to melt above about100° C. For example, melting point categories used by one pharmaceuticalcompany are, in order of preference, +(mp>120° C.), 0 (mp 80-120° C.),and −(mp<80° C.) (Balbach, S.; Korn, C. Int. J. Pharmaceutics 2004 2751-12).

Active drug molecules may be made into pharmaceutically acceptable saltsfor therapeutic administration to the patient. Crystalline salts of adrug may offer advantages over the free form of the compound, such asimproved solubility, stability, processing improvements, etc., anddifferent crystalline salt forms may offer greater or lesser advantagesover one another. However, crystalline salt formation is notpredictable, and in fact is not always possible. Moreover, there is noway to predict the properties of a particular crystalline salt of acompound until it is formed. As such, finding the right conditions toobtain a particular crystalline salt form of a compound, withpharmaceutically acceptable properties, can take significant time andeffort.

It is also possible to achieve desired properties of a particular API byforming a cocrystal of the API itself, or of a salt of the API.Cocrystals are crystals that contain two or more non-identicalmolecules. Examples of cocrystals may be found in the CambridgeStructural Database. Examples of cocrystals may also be found at Etter,M. C., and Adsmond, D. A., J. Chem. Soc., Chem. Commun. 1990 589-591;Etter, M. C., MacDonald, J. C., and Bernstein, J., Acta Crystallogr.,Sect. B, Struct. Sci. 1990 B46 256-262; and Etter, M. C.,Urbańczyk-Lipkowska, Z., Zia-Ebrahimi, M., and Panunto, T. W., J. Am.Chem. Soc. 1990 112 8415-8426, which are incorporated herein byreference in their entireties. The following articles are alsoincorporated herein by reference in their entireties: Görbotz C. H., andHersleth, H. P. Acta Cryst. 2000 B56 625-534; and Senthil Kumar, V. S.,Nangia, A., Katz, A. K., and Carrell, H. L., Crystal Growth & Design,2002 2 313-318.

By cocrystallizing an API, or a salt of an API, with a co-former (theother component of the cocrystal), one creates a new solid state form ofthe API which has unique properties compared with existing solid formsof the API or its salt. For example, a cocrystal may have differentdissolution and/or solubility properties than the active agent itself orits salt. Cocrystals containing APIs can be used to deliver APIstherapeutically. New drug formulations comprising cocrystals of APIswith pharmaceutically acceptable co-formers may, in some cases, havesuperior properties over existing drug formulations. However, cocrystalformation is not predictable, and in fact is not always possible.Moreover, there is no way to predict the properties of a particularcocrystal of a compound until it is formed. As such, finding the rightconditions to obtain a particular cocrystal of a compound, withpharmaceutically acceptable properties, can take significant time,effort, and resources.

A crystalline form of a compound, a crystalline salt of the compound, ora cocrystal containing the compound or its salt form generally possessesdistinct crystallographic and spectroscopic properties when compared toother crystalline forms having the same chemical composition.Crystallographic and spectroscopic properties of a particular form maybe measured by XRPD, single crystal X-ray crystallography, solid stateNMR spectroscopy, e.g. ¹³C CP/MAS NMR, or Raman spectrometry, amongother techniques. A particular crystalline form of a compound, of itssalt, or of a cocrystal, often also exhibits distinct thermal behavior.Thermal behavior can be measured in the laboratory by such techniquesas, for example, capillary melting point, TGA, and DSC.

In the following description, various aspects and embodiments of theinvention will become evident. In its broadest sense, the inventioncould be practiced without having one or more features of these aspectsand embodiments. Further, these aspects and embodiments are exemplary.Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practicing of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

SUMMARY

In accordance with various embodiments of the invention and afterextensive experimentation, the inventors have discovered novelcrystalline salt forms of epalrestat, including a potassium anhydratesalt, a sodium anhydrate salt, and a 1-(2-hydroxyethyl)-pyrrolidineanhydrate salt. In accordance with further various embodiments of theinvention, the inventors have discovered a novel betaine cocrystal ofepalrestat, betaine hydrogen diepalrestat.

The invention in various embodiments also relates to processes ofpreparing those novel crystalline salts and cocrystal of epalrestat,pharmaceutical compositions containing them, and their use in thetreatment and/or prevention of various conditions such as diabeticcomplications, and also to afford cardioprotection in patients who maybe non-diabetic.

As used herein, the term “XRPD” refers to x-ray powder diffraction. TheXRPD data disclosed herein were obtained using an Inel XRG-3000diffractometer equipped with a CPS (Curved Position Sensitive) detectorwith a 2θ range of 120°. Real time data were collected using Cu-Kαradiation at a resolution of 0.03° 2θ. The tube voltage and amperagewere set to 40 kV and 30 mA, respectively. The monochromator slit wasset at 5 mm by 160 μm. Samples were prepared for analysis by packingthem into thin-walled glass capillaries. Each capillary was mounted ontoa goniometer head that is motorized to permit spinning of the capillaryduring data acquisition. Instrument calibration was performed using asilicon reference standard.

As used herein, the term “DSC” refers to differential scanningcalorimetry. DSC data disclosed herein were obtained using a TAInstruments differential scanning calorimeter 2920. The sample wasplaced into an aluminum DSC pan, and the weight accurately recorded. Thepan was crimped with manual pin hole. The sample cell was equilibratedat 25° C. then heated under a nitrogen purge at a rate of 10° C./min, upto a final temperature of 300 or 325° C. Indium metal was used as thecalibration standard.

As used herein, the term “¹H-NMR” refers to proton nuclear magneticresonance spectroscopy. Solution ¹H NMR data disclosed herein wereacquired at ambient temperature on a Varian ^(UNITY)INOVA-400spectrometer (¹H Larmor Frequency=399.8 MHz). The samples were dissolvedin NMR-grade dimethyl sulfoxide containing 0.03% TMS. Each ¹H NMRspectrum represents 40 co-added transients collected with either an 8.1or 6.01 μsec pulse and a relaxation delay time of 5 seconds. The freeinduction decay (FID) was exponentially multiplied with a 0.2 HzLorentzian line broadening factor to improve the signal-to-noise ratio.

As used herein, the term “TGA” refers to thermogravimetric analysis. TGAdata disclosed herein were obtained using a TA Instruments 2950thermogravimetric analyzer. Each sample was placed in an aluminum samplepan and inserted into the TG furnace. The furnace was first equilibratedat 25° C. and then heated under nitrogen at a rate of 10° C./min, up toa final 1 temperature of 350° C. Nickel and Alumel™ were used as thecalibration standards.

As used herein, the term “DVS” refers to dynamic vapor sorption. DVSdata disclosed herein were obtained using a VTI SGA-100 Vapor SorptionAnalyzer. Sorption and desorption data were collected over a range of 5%to 95% relative humidity (“RH”), at 10% RH intervals under a nitrogenpurge. Samples were not dried prior to analysis. Equilibrium criteriaused for analysis were less than 0.0100% weight change in 5 minutes,with a maximum equilibration time of 3 hours if the weight criterion wasnot met. Data were not corrected for the initial moisture content of thesamples. NaCl and PVP were used as calibration standards.

As shown herein, solubility data were collected in water at ambienttemperature using an orbital shaker. Samples were taken at approximately1, 3, 6, and 24 hours, and analyzed by UV spectrophotometry using aSpectraMax M2 Microplate Reader. Wavelength calibration and photometricaccuracy were performed using the SpectraMax Pro 5 software as aninternal calibration of the instrument. The detector was zeroed with areference well on a microplate filled with water on which data wasobtained, and that data was subtracted from collected data. Samples wereanalyzed in the UV range at room temperature in the wells of a 96-wellquartz plate.

As used herein with respect to the various analytical techniquesdescribed herein and data generated therefrom, the term “substantially”the same as or similar to is meant to convey that a particular set ofanalytical data is, within acceptable scientific limits, sufficientlysimilar to that disclosed herein such that one of skill in the art wouldappreciate that the crystal salt form of the compound is the same asthat of the present invention. One of skill in the art would appreciatethat certain analytical techniques, such as XRPD, ¹H-NMR, DSC, TGA, DVS,and UV spectrophotometry will not produce exactly the same results everytime due to, for example, instrumental variation, sample preparation,scientific error, etc. By way of example only, XRPD results (i.e. peaklocations, intensities, and/or presence) may vary slightly from sampleto sample, despite the fact that the samples are, within acceptedscientific principles, the same form, and this may be due to, forexample, preferred orientation or varying solvent or water content. Itis well within the ability of those skilled in the art, looking at thedata as a whole, to appreciate whether such differences indicate adifferent form, and thus determine whether analytical data beingcompared to those disclosed herein are substantially similar. In thisregard, and as is commonly practiced within the scientific community, itis not intended that the exemplary analytical data of the novel salts ofepalrestat disclosed herein be met literally in order to determinewhether comparative data represent the same form as those disclosed andclaimed herein, such as, for example, whether each and every peak of anexemplary XRPD pattern of a novel salt or cocrystal of epalrestatdisclosed herein is present in the comparative data, in the samelocation, and/or of the same intensity. Rather, as discussed above, itis intended that those of skill in the art, using accepted scientificprinciples, will make a determination based on the data as a wholeregarding whether comparative analytical data represent the same or adifferent form of any of the novel crystalline salts of epalrestat orthe novel betaine hydrogen diepalrestat cocrystal disclosed herein.

As used herein, “hep” means hydroxyethylpyrrolidone.

As used herein, the terms “betaine hydrogen diepalrestat” and “betainehydrogen diacid cocrystal of epalrestat,” including variations which usethe chemical name“5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineaceticacid” in place of the common name “epalrestat,” are used interchangeablyto refer to the novel betaine cocrystal of epalrestat described herein.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an XRPD pattern of a crystalline potassium anhydrate salt ofepalrestat, according to one embodiment of the invention;

FIG. 2 is an XRPD pattern of a crystalline sodium anhydrate salt ofepalrestat, according to one embodiment of the invention;

FIG. 3 is an XRPD pattern of a crystalline1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of epalrestat, accordingto one embodiment of the invention;

FIG. 4 is an XRPD pattern of a betaine hydrogen diacid cocrystal ofepalrestat, according to one embodiment of the invention;

FIG. 5 is a DSC thermogram of a crystalline potassium anhydrate salt ofepalrestat, according to one embodiment of the invention;

FIG. 6 is a DSC thermogram of a crystalline sodium anhydrate salt ofepalrestat, according to one embodiment of the invention;

FIG. 7 is a DSC thermogram of a crystalline1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of epalrestat, accordingto one embodiment of the invention;

FIG. 8 is a DSC thermogram of a betaine hydrogen diacid cocrystal ofepalrestat, according to one embodiment of the invention;

FIG. 9A is a full ¹H-NMR spectrum of a crystalline potassium anhydratesalt of epalrestat, according to one embodiment of the invention;

FIG. 9B is an ¹H-NMR spectrum from 8.1 to 6.8 ppm of a crystallinepotassium anhydrate salt of epalrestat, according to one embodiment ofthe invention;

FIG. 9C is an ¹H-NMR spectrum from 4.6 to 2.1 ppm of a crystallinepotassium anhydrate salt of epalrestat, according to one embodiment ofthe invention;

FIG. 9D is an ¹H-NMR spectrum from 1.9 to 1.0 ppm of a crystallinepotassium anhydrate salt of epalrestat, according to one embodiment ofthe invention;

FIG. 10A is a full ¹H-NMR spectrum of a crystalline sodium anhydratesalt of epalrestat, according to one embodiment of the invention;

FIG. 10B is an ¹H-NMR spectrum from 10.25 to 9.95 ppm of a crystallinesodium anhydrate salt of epalrestat, according to one embodiment of theinvention;

FIG. 10C is an ¹H-NMR spectrum from 8.0 to 7.14 ppm of a crystallinesodium anhydrate salt of epalrestat, according to one embodiment of theinvention;

FIG. 10D is an ¹H-NMR spectrum from 4.5 to 1.5 ppm of a crystallinesodium anhydrate salt of epalrestat, according to one embodiment of theinvention;

FIG. 11A is a full ¹H-NMR spectrum of a crystalline1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of epalrestat, accordingto one embodiment of the invention;

FIG. 11B is an ¹H-NMR spectrum from 8.0 to 7.2 ppm of a crystalline1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of epalrestat, accordingto one embodiment of the invention;

FIG. 11C is an ¹H-NMR spectrum from 4.8 to 2.8 ppm of a crystalline1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of epalrestat, accordingto one embodiment of the invention;

FIG. 11D is an ¹H-NMR spectrum from 3.0 to 1.4 ppm of a crystalline1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of epalrestat, accordingto one embodiment of the invention;

FIG. 12A is a full ¹H-NMR spectrum of a betaine hydrogen diacidcocrystal of epalrestat, according to one embodiment of the invention;

FIG. 12B is an ¹H-NMR spectrum from 15.0 to 13.6 ppm of a betainehydrogen diacid cocrystal of epalrestat, according to one embodiment ofthe invention;

FIG. 12C is an ¹H-NMR spectrum from 8.2 to 7.2 ppm of a betaine hydrogendiacid cocrystal of epalrestat, according to one embodiment of theinvention;

FIG. 12D is an ¹H-NMR spectrum from 5.2 to 2.0 ppm of a betaine hydrogendiacid cocrystal of epalrestat, according to one embodiment of theinvention;

FIG. 13 is a TGA profile of a crystalline potassium anhydrate salt ofepalrestat, according to one embodiment of the invention;

FIG. 14 is a TGA profile of a crystalline sodium anhydrate salt ofepalrestat, according to one embodiment of the invention; and

FIG. 15 is a TGA profile of a crystalline 1-(2-hydroxyethyl)-pyrrolidineanhydrate salt of epalrestat, according to one embodiment of theinvention.

FIG. 16 is a TGA profile of a betaine hydrogen diacid cocrystal ofepalrestat, according to one embodiment of the invention; and.

FIG. 17 is a DVS profile of a betaine hydrogen diacid cocrystal ofepalrestat, according to one embodiment of the invention.

FIGS. 18A-18B show solubility data for a betaine hydrogen diacidcocrystal of epalrestat, according to one embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

One aspect of the invention described herein relates to novelcrystalline salt forms of epalrestat. Specifically, the novelcrystalline salts which have been discovered include a potassiumanhydrate salt, a sodium anhydrate salt, and a1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of epalrestat. Exemplarymethods of preparation of the novel crystalline salt forms of epalrestataccording to various embodiments of the invention are described below inthe examples.

All of the inventive salts of epalrestat as described herein can beobtained in a crystalline solid form. The salts of the invention aredescribed as crystalline because of the high degree of crystallinity ofthe forms as depicted by the XRPD patterns provided in FIGS. 1-3. Theforms are shown to have distinct physicochemical properties. The novelcrystalline salt forms of epalrestat according to various embodiments ofthe invention are particularly suitable for the preparation of stablepharmaceutical preparations.

The crystalline potassium anhydrate salt of epalrestat is characterizedby an XRPD pattern substantially as shown in FIG. 1, a DSC thermogramsubstantially as shown in FIG. 5, ¹H-NMR spectra substantially as shownin FIGS. 9A-9D, and a TGA profile substantially as shown in FIG. 13. Anexemplary listing of representative XRPD peaks of a crystallinepotassium anhydrate salt of epalrestat according to the invention can befound in Table 1. Prominent XRPD peaks may include, in one exemplaryembodiment, peaks at 3.8, 15.4, and 15.7° 2θ±0.2. An exemplary listingof representative NMR data can be found in Table 2.

TABLE 1 °2θ d space (Å) Intensity (%)  3.8 ± 0.2 22.95 ± 1.22  100  7.8± 0.2 11.36 ± 0.30  3 15.4 ± 0.2 5.74 ± 0.07 11 15.7 ± 0.2 5.63 ± 0.0711 17.8 ± 0.2 4.98 ± 0.06 2 19.4 ± 0.2 4.56 ± 0.05 3 20.2 ± 0.2 4.39 ±0.04 6 21.4 ± 0.2 4.15 ± 0.04 7 22.6 ± 0.2 3.94 ± 0.03 2 23.3 ± 0.2 3.82± 0.03 17 24.1 ± 0.2 3.69 ± 0.03 31 25.2 ± 0.2 3.54 ± 0.03 3 26.3 ± 0.23.39 ± 0.03 3 27.5 ± 0.2 3.25 ± 0.02 11 28.8 ± 0.2 3.11 ± 0.02 3

TABLE 2 number peak coupling of protons position (ppm) multiplicityconstant (Hz) protons CH₃ 2.21 doublet 1 3 CH₂ 4.24 singlet — 2olefin/aromatic 7.32 broad singlet — 1 olefin/aromatic 7.35-7.39multiplet — 1 olefin/aromatic 7.42-7.49 multiplet — 4 olefin 7.51doublet 1 1

The crystalline sodium anhydrate salt of epalrestat is characterized byan XRPD pattern substantially as shown in FIG. 2, a DSC thermogramsubstantially as shown in FIG. 6, ¹H-NMR spectra substantially as shownin FIGS. 10A-10D, and a TGA profile substantially as shown in FIG. 14.An exemplary listing of representative XRPD peaks of a crystallinesodium anhydrate salt of epalrestat according to the invention can befound in Table 3. Prominent XRPD peaks may include, in one exemplaryembodiment, peaks at 3.7, 17.3, and 18.2° 2θ±0.2. An exemplary listingof representative NMR data can be found in Table 4.

TABLE 3 °2θ d space (Å) Intensity (%)  3.7 ± 0.2 24.08 ± 1.35  100  7.4± 0.2 11.91 ± 0.33  2 11.2 ± 0.2 7.90 ± 0.14 2 12.9 ± 0.2 6.86 ± 0.11 315.7 ± 0.2 5.63 ± 0.07 5 16.1 ± 0.2 5.52 ± 0.07 5 16.6 ± 0.2 5.34 ± 0.065 17.3 ± 0.2 5.12 ± 0.06 21 18.2 ± 0.2 4.88 ± 0.05 12 18.5 ± 0.2 4.79 ±0.05 2 19.2 ± 0.2 4.61 ± 0.05 6 20.4 ± 0.2 4.36 ± 0.04 5 21.6 ± 0.2 4.11± 0.04 3 23.2 ± 0.2 3.83 ± 0.03 8 23.9 ± 0.2 3.72 ± 0.03 25 24.4 ± 0.23.65 ± 0.03 17 25.1 ± 0.2 3.55 ± 0.03 5 25.7 ± 0.2 3.47 ± 0.03 2 26.6 ±0.2 3.35 ± 0.02 17 27.5 ± 0.2 3.25 ± 0.02 4 28.5 ± 0.2 3.13 ± 0.02 828.8 ± 0.2 3.10 ± 0.02 3 29.5 ± 0.2 3.03 ± 0.02 2

TABLE 4 number peak coupling of protons position (ppm) multiplicityconstant (Hz) protons CH₃ 2.21 doublet 1 3 CH₂ 4.27 singlet — 2olefin/aromatic 7.29-7.34 multiplet — 1 olefin/aromatic 7.35-7.41multiplet — 1 olefin/aromatic 7.42-7.49 multiplet — 4

The crystalline 1-(2-hydroxyethyl)-pyrrolidine anhydrate salt ofepalrestat is characterized by an XRPD pattern substantially as shown inFIG. 3, a DSC thermogram substantially as shown in FIG. 7, ¹H-NMRspectra substantially as shown in FIGS. 11A-11D, and a TGA profilesubstantially as shown in FIG. 15. An exemplary listing ofrepresentative XRPD peaks of a crystalline1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of epalrestat according tothe invention can be found in Table 5. Prominent XRPD peaks may include,in one exemplary embodiment, peaks at 6.7, 10.5, 11.5, and 14.2° 2θ±0.2.An exemplary listing of representative NMR data can be found in Table 6.

TABLE 5 °2θ d space (Å) Intensity (%)  6.7 ± 0.2 13.13 ± 0.40  13  8.6 ±0.2 10.22 ± 0.24  5 10.5 ± 0.2 8.44 ± 0.16 22 11.5 ± 0.2 7.70 ± 0.13 2713.4 ± 0.2 6.58 ± 0.10 5 14.2 ± 0.2 6.24 ± 0.09 64 14.7 ± 0.2 6.02 ±0.08 13 15.2 ± 0.2 5.81 ± 0.08 17 16.6 ± 0.2 5.34 ± 0.06 23 17.0 ± 0.25.20 ± 0.06 9 18.0 ± 0.2 4.94 ± 0.05 21 19.9 ± 0.2 4.47 ± 0.04 9 20.2 ±0.2 4.39 ± 0.04 10 20.6 ± 0.2 4.31 ± 0.04 19 21.0 ± 0.2 4.24 ± 0.04 1522.3 ± 0.2 3.99 ± 0.04 100 22.8 ± 0.2 3.89 ± 0.03 27 23.4 ± 0.2 3.80 ±0.03 22 23.8 ± 0.2 3.74 ± 0.03 20 24.4 ± 0.2 3.64 ± 0.03 10 24.8 ± 0.23.58 ± 0.03 3 25.8 ± 0.2 3.45 ± 0.03 15 27.5 ± 0.2 3.25 ± 0.02 11 27.9 ±0.2 3.20 ± 0.02 41 28.3 ± 0.2 3.15 ± 0.02 8 28.6 ± 0.2 3.12 ± 0.02 828.9 ± 0.2 3.09 ± 0.02 6 29.2 ± 0.2 3.06 ± 0.02 5 29.6 ± 0.2 3.01 ± 0.0210

TABLE 6 peak coupling number of protons position (ppm) multiplicityconstant (Hz) protons CH₂ (hep) 1.79-1.86 multiplet — 41.03 (4) CH₃ 2.22doublet 1 30.32 (3) CH₂ (hep) 2.97-3.03 multiplet — 61.72 (6) CH₂ (hep)3.62 triplet 5 20.95 (2) CH₂ 4.45 singlet — 20.36 (2) olefin/ 7.35-7.39multiplet — 20.66 (2) aromatic olefin/ 7.43-7.49 multiplet — 40.69 (4)aromatic olefin 7.56 doublet 1 10.00 (1)

A further aspect of the invention described herein relates to a novelbetaine cocrystal of epalrestat. Specifically, the novel cocrystal whichhas been discovered is a betaine hydrogen diacid cocrystal of epalrestathaving approximately two moles of epalrestat and approximately one moleof betaine. In one embodiment, the novel cocrystal is anhydrous.Exemplary methods of preparation of the novel betaine cocrystal ofepalrestat according to the invention are described below in theexamples.

The novel cocrystal described herein is obtained in a crystalline solidform, as seen by the high degree of crystallinity depicted in the XRPDpattern provided in FIG. 4. The cocrystal is shown to have distinctphysicochemical properties and is stable to decomposition from uptake ofmoisture at specified conditions. The cocrystal of epalrestat describedherein is particularly suitable for the preparation of stablepharmaceutical preparations.

The novel betaine cocrystal of epalrestat is characterized by an XRPDpattern substantially as shown in FIG. 4, a DSC thermogram substantiallyas shown in FIG. 8, ¹H-NMR spectra substantially as shown in FIGS.12A-12D, a TGA profile substantially as shown in FIG. 16, and asolubility profile substantially as shown in FIG. 18A.

An exemplary listing of representative XRPD peaks of the novel betainecocrystal of epalrestat according to the invention can be found in Table7. Prominent XRPD peaks may include, in one exemplary embodiment, peaksat 6.0, 12.2, 13.1, 14.0, and 15.0° 2θ±0.2. An exemplary listing ofrepresentative NMR data can be found in Table 8.

TABLE 7 °2θ d space (Å) Intensity (%)  6.0 ± 0.2 14.71 ± 0.50  90 12.2 ±0.2 7.23 ± 0.12 15 12.7 ± 0.2 6.95 ± 0.11 13 13.1 ± 0.2 6.76 ± 0.10 6114.0 ± 0.2 6.33 ± 0.41 22 14.4 ± 0.2 6.13 ± 0.09 9 15.0 ± 0.2 5.91 ±0.08 77 16.1 ± 0.2 5.51 ± 0.07 29 16.4 ± 0.2 5.42 ± 0.07 30 16.8 ± 0.25.27 ± 0.06 25 18.1 ± 0.2 4.91 ± 0.05 23 18.5 ± 0.2 4.79 ± 0.05 23 19.1± 0.2 4.65 ± 0.05 34 20.4 ± 0.2 4.35 ± 0.04 18 21.0 ± 0.2 4.24 ± 0.04 1021.4 ± 0.2 4.15 ± 0.04 37 21.8 ± 0.2 4.08 ± 0.04 100 22.1 ± 0.2 4.02 ±0.04 38 22.5 ± 0.2 3.95 ± 0.03 11 22.9 ± 0.2 3.88 ± 0.03 8 23.5 ± 0.23.78 ± 0.03 6 24.0 ± 0.2 3.72 ± 0.03 12 24.3 ± 0.2 3.66 ± 0.03 31 24.8 ±0.2 3.60 ± 0.03 37 25.5 ± 0.2 3.49 ± 0.03 80 25.8 ± 0.2 3.45 ± 0.03 4326.2 ± 0.2 3.40 ± 0.03 13 26.5 ± 0.2 3.36 ± 0.03 44 27.5 ± 0.2 3.24 ±0.02 12 28.2 ± 0.2 3.17 ± 0.02 35 28.5 ± 0.2 3.13 ± 0.02 10 28.8 ± 0.23.10 ± 0.02 18 29.8 ± 0.2 3.00 ± 0.02 8

TABLE 8 peak number of protons position (ppm) multiplicity protons CH₃2.22 singlet 6 CH₃ (betaine) 3.15 singlet 9 CH₂ (betaine) 3.70 singlet 2CH₂ 4.70 singlet 4 olefin/aromatic 7.36-7.40 multiplet 4 olefin/aromatic7.43-7.49 multiplet 8 olefin 7.62 singlet 2

In various embodiments, the novel betaine cocrystal of epalrestatdescribed herein is stable. For example, no change in the XRPD patternwas seen when the material was compressed into a disk at 3400 pounds ofpressure (117 MPa pressure) for 1 minute, using a Carver hydraulic pressand pellet die.

Pharmaceutical Compositions and Methods of Treatment and/or Prevention

The novel crystalline salt forms of epalrestat and novel betainecocrystal of epalrestat according to various embodiments of theinvention possess the same general pharmacological activity asepalrestat free acid, and are useful for treating and/or preventingdiabetic complications such as those discussed above, including, forexample, diabetic neuropathy, diabetic retinopathy, and diabeticnephropathy. By use of the term “treating” or “alleviating” it is meantdecreasing the symptoms, markers, or any negative effects of a conditionin any appreciable degree in a patient who currently has the condition,and by “preventing” it is meant preventing entirely or preventing tosome extent, such as, for example, by delaying the onset or lesseningthe degree to which a patient develops the condition.

Accordingly, various embodiments of the invention include methods forpreventing and/or treating cardiac tissue ischemia in a mammalcomprising administering to said mammal an effective amount ofepalrestat comprising one or more of the novel crystalline salt forms ofepalrestat and/or the novel betaine cocrystal of epalrestat describedherein. Various embodiments of the invention also include methods fortreating and/or preventing cardiac tissue ischemia in a mammalcomprising administering to said mammal a pharmaceutical compositioncomprising at least some amount of at least one novel crystalline saltform of epalrestat described herein and/or the novel betaine cocrystalof epalrestat described herein, and a pharmaceutically acceptablevehicle, carrier, and/or diluent. In exemplary methods, said mammal maybe suffering from cardiac tissue ischemia or may be at risk of sufferingfrom cardiac tissue ischemia. For example, a mammal at risk may beawaiting or undergoing cardiac, cardiovascular, or other major surgery.Thus, various embodiments of the invention include methods for providingmyocardial protection during surgery or myocardial protection inpatients presenting with ongoing cardiac or cerebral ischemic events orchronic cardioprotection in patients diagnosed with, or at risk for,coronary heart disease, cardiac dysfunction or myocardial stunning. Asused herein, “mammal” is intended to include humans.

Various embodiments of the invention include methods of inhibitingaldose reductase in a mammal in need of inhibition of aldose reductasecomprising administering an aldose reductase inhibiting amount ofepalrestat comprising at least one of the novel crystalline salt formsof epalrestat and/or novel betaine cocrystal of epalrestat as describedherein. Various embodiments of the invention also include methods ofinhibiting aldose reductase in a mammal in need of inhibition of aldosereductase, comprising administering a pharmaceutical compositioncomprising at least one novel crystalline salt form of epalrestat and/ornovel betaine cocrystal of epalrestat as described herein, and apharmaceutically acceptable vehicle, carrier, and/or diluent.

Additional embodiments of the invention include methods of treatingand/or preventing one or more diabetic complications in a mammalsuffering from one or more diabetic complications comprisingadministering to said mammal an effective amount of epalrestatcomprising at least one novel crystalline salt form of epalrestat and/ornovel betaine cocrystal of epalrestat as described herein. Diabeticcomplications which may be treated and/or prevented by exemplary methodsof the invention include, but are not limited to, diabetic neuropathy,diabetic nephropathy, diabetic cardiomyopathy, cardiac autonomicneuropathy, diabetic retinopathy, diabetic macular edema, diabeticgastroparesis, cataracts, foot ulcers, diabetic macroangiopathy, anddiabetic microangiopathy. Various embodiments of the invention are alsodirected to methods of treating and/or preventing one or more diabeticcomplications in a mammal suffering from one or more diabeticcomplications comprising administering to said mammal an effectiveamount of a pharmaceutical composition as set forth herein.

Further embodiments of the invention contemplate methods of treatingand/or preventing homocystinuria, and/or reducing levels of homocysteinein the blood serum, for example in a patient with diabetes, byadministering an effective amount of epalrestat comprising the novelbetaine cocrystal of epalrestat, or composition and/or formulationcomprising an effective amount of epalrestat comprising the novelbetaine cocrystal of epalrestat, as described herein. Betaine, alsoknown as trimethylglycine or glycine betaine, is a naturally occurringmolecule found in dietary sources (Olthof M R, Curr Drug Metab 2005;6:15-22). In biological systems, betaine is important in the metabolismof homocysteine, and functions as a methyl donor. Betaine is thereforeused therapeutically to reduce elevated homocysteine concentrations (vanGuldener C et al, Expert Opinion on Pharmacotherapy 2001; 2:1449-1460),and is approved for use in the U.S. and Europe as a therapeutic agent totreat homocystinuria from genetic causes (Cystadane prescribinginformation, FDA; Cystadane product information, EMEA). Elevatedhomocysteine is associated with cardiovascular disease in both Type 2diabetes (Hoogeveen E K et al, Arterioscler Thromb Vasc Biol 1998;18:133-138) and in non-diabetic populations (Bostom A G et al, ArchIntern Med 1999; 159:1077-1080). Homocysteine is also elevated inpatients with various non-cardiovascular diabetic complications,including diabetic nephropathy (Bostom A G et al, Arterioscler ThrombVasc Biol 1997; 17:2554-2558), diabetic retinopathy (Brazionis L et al,Diabetes Care 2008; 31:50-56), and diabetic neuropathy (Ambrosch A etal, Diabetic Medicine 2001; 18:185-192). Administration of a novelbetaine cocrystal of epalrestat may, therefore, have an additionalbeneficial therapeutic effect for treating these conditions. Forexample, administration of the combination of epalrestat and betaine asin the novel cocrystal of the invention, for example to a diabeticpatient, may have a synergistic effect that is greater than the effectsof administering epalrestat and/or betaine alone.

Various additional embodiments of the invention include methods ofpalliating neurological disorders and delaying development ofneurological disorders by administering aldose reductase inhibitors,including the novel crystalline salts of epalrestat and/or novel betainecocrystal of epalrestat described herein, in order to modulateneurotrophic factor-associated activity, especially CNTF-associatedlevels and activity, for example as disclosed in U.S. Pat. No.6,696,407. These methods are useful, for example, for a condition orcircumstance in which neurotrophic factor-associated activity isindicated, such as neurological disorders, including neurodegenerativedisorders. A “neurological disorder” as used herein means an aberrationfrom clinically normal neural cell activity (i.e., compromised neuralcell activity) and includes, by way of example only, neurodegenerativedisease (of the CNS and/or PNS), neuropathies associated with toxicity(neurotoxicity) such as chemotherapy (i.e., vincristine orcisplatin-induced motor neuropathy) and alcohol consumption,immune-mediated neurodiseases such as multiple sclerosis (MS) andGuillain-Barre syndrome, hereditary neuropathies such asCharcot-Marie-Tooth neuropathies [see Lebo et al. (1992) Am. J. Hum.Genet. 50:42-55], injury due to trauma, and compromised function due tosenescence. Examples of neurodegenerative disorders include but are notlimited to, Huntington's disease, amyotrophic lateral sclerosis (ALS),Alzheimer's disease, Parkinson's disease, and Shy-Drager syndrome. Themethods may also be useful in delaying development of a neurologicaldisorder, and thus may be used in individuals who show no overt signs ofdisease but are, for example, at risk of developing disease.

As discussed, additional embodiments of the invention relate topharmaceutical compositions comprising a therapeutically effectiveamount of one or more novel crystalline salts of epalrestat and/or novelbetaine cocrystal of epalrestat according to various embodiments of theinvention and a pharmaceutically acceptable carrier or excipient. Thenovel crystalline salts of epalrestat and/or novel betaine cocrystal ofepalrestat according to various embodiments of the invention have thesame or similar pharmaceutical activity as previously reported forepalrestat free acid. Pharmaceutical compositions for the treatmentand/or prevention of those conditions or disorders may contain someamount, for example a therapeutically effective amount, of one or moreof the novel crystalline salts of epalrestat and/or novel betainecocrystal of epalrestat described herein, as appropriate, e.g. fortreatment of a patient with the particular condition or disorder. As afurther example, the amount of the one or more of the novel crystallinesalts of epalrestat and/or novel betaine cocrystal of epalrestat in thepharmaceutical compositions may likewise be lower than a therapeuticallyeffective amount, and may, for example, be in the composition inconjunction with another compound or form of epalrestat which, whencombined, are present in a therapeutically effective amount. A“therapeutically effective amount” as described herein refers to anamount of a therapeutic agent sufficient to treat, alleviate, and/orprevent a condition treatable and/or preventable by administration of acomposition of the invention, in any degree. That amount can be anamount sufficient to exhibit a detectable therapeutic or preventative orameliorative effect, and can be determined by routine experimentation bythose of skill in the art. The effect may include, for example,treatment, alleviation, and/or prevention of the conditions listedherein. The actual amount required, e.g. for treatment of any particularpatient, will depend upon a variety of factors including the disorderbeing treated and/or prevented; its severity; the specificpharmaceutical composition employed; the age, body weight, generalhealth, gender, and diet of the patient; the mode of administration; thetime of administration; the route of administration; the rate ofexcretion of epalrestat; the duration of the treatment; any drugs usedin combination or coincidental with the specific compound employed; andother such factors well known in the medical arts. These factors arediscussed in Goodman and Gilman's “The Pharmacological Basis ofTherapeutics”, Tenth Edition, A. Gilman, J. Hardman and L. Limbird,eds., McGraw-Hill Press, 155-173, 2001.

A pharmaceutical composition according to various embodiments of theinvention may be any pharmaceutical form which contains one or morenovel crystalline salts of epalrestat and/or novel betaine cocrystal ofepalrestat according to various embodiments of the invention. Dependingon the type of pharmaceutical composition, the pharmaceuticallyacceptable carrier may be chosen from any one or a combination ofcarriers known in the art. The choice of the pharmaceutically acceptablecarrier depends upon the pharmaceutical form and the desired method ofadministration to be used. For a pharmaceutical composition according tovarious embodiments of the invention, that is one having one or more ofthe novel crystalline salts of epalrestat and/or novel betaine cocrystalof epalrestat described herein, a carrier may be chosen that maintainsthe crystalline salt form or cocrystal form. In other words, thecarrier, in some embodiments, will not substantially alter thecrystalline form of the crystalline salts of epalrestat or novel betainecocrystal of epalrestat as described herein. In certain embodiments, thecarrier will similarly not be otherwise incompatible with epalrestatitself, crystalline salts of epalrestat, or novel betaine cocrystal ofepalrestat according to various embodiments of the invention, such as byproducing any undesirable biological effect or otherwise interacting ina deleterious manner with any other component(s) of the pharmaceuticalcomposition.

The pharmaceutical compositions according to various embodiments of theinvention are optionally formulated in unit dosage form for ease ofadministration and uniformity of dosage. A “unit dosage form” refers toa physically discrete unit of therapeutic agent appropriate for thepatient to be treated. It will be understood, however, that the totaldaily dosage of the novel crystalline salts of epalrestat and/or novelbetaine cocrystal of epalrestat according to various embodiments of theinvention and pharmaceutical compositions thereof will be decided by theattending physician within the scope of sound medical judgment usingknown methods.

Because the crystalline form of the novel crystalline salts ofepalrestat and novel betaine cocrystal of epalrestat described herein ismore easily maintained during preparation, solid dosage forms are apreferred form for the pharmaceutical composition of the invention.Solid dosage forms for oral administration may include, for example,capsules, tablets, pills, powders, and granules. In one exemplaryembodiment, the solid dosage form is a tablet. The active ingredient maybe contained in a solid dosage form formulation that provides quickrelease, sustained release, or delayed release after administration tothe patient. In such solid dosage forms, the active compound may bemixed with at least one inert, pharmaceutically acceptable carrier, suchas, for example, sodium citrate or dicalcium phosphate. The solid dosageform may also include one or more of various additional ingredients,including, for example: a) fillers or extenders such as, for example,starches, lactose, sucrose, glucose, mannitol, and silicic acid; b)binders such as, for example, carboxymethylcellulose, alginates,gelatin, polyvinylpyrrolidinone, sucrose, and acacia; c) humectants suchas, for example, glycerol; d) disintegrating agents such as, forexample, agar, calcium carbonate, potato or tapioca starch, alginicacid, certain silicates, and sodium carbonate; e) dissolution retardingagents such as, for example, paraffin; f) absorption accelerators suchas, for example, quaternary ammonium compounds; g) wetting agents suchas, for example, cetyl alcohol and glycerol monostearate; h) absorbentssuch as, for example, kaolin and bentonite clay; and i) lubricants suchas, for example, talc, calcium stearate, magnesium stearate, solidpolyethylene glycols, and sodium lauryl sulfate. The solid dosage formsmay also comprise buffering agents. They may optionally containopacifying agents and can also be of a composition that they release theactive ingredient(s) only, or preferentially, in a certain part of theintestinal tract, optionally, in a delayed manner. Remington'sPharmaceutical Sciences, Sixteenth Edition, E. W. Martin (MackPublishing Co., Easton, Pa., 1980) discloses various carriers used informulating pharmaceutical compositions and known techniques for thepreparation thereof. Solid dosage forms of pharmaceutical compositionsaccording to various embodiments of the invention can also be preparedwith coatings and shells such as enteric coatings and other coatingswell known in the pharmaceutical formulating art.

The novel crystalline salts of epalrestat and novel betaine cocrystal ofepalrestat according to various embodiments of the invention can be, forexample, administered in a solid micro-encapsulated form with one ormore carriers as discussed above. Microencapsulated forms may also beused in soft and hard-filled gelatin capsules with carriers such aslactose or milk sugar as well as high molecular weight polyethyleneglycols and the like.

The novel crystalline salts of epalrestat and novel betaine cocrystal ofepalrestat according to various embodiments of the invention may also beused in the preparation of non-solid formulations, e.g., injectables andpatches, of epalrestat. Such non-solid formulations are known in theart. In a non-solid formulation, the crystalline salt form and/orcocrystal form may, in certain exemplary embodiments, not be maintained.For example, the crystalline salt form may be dissolved in a liquidcarrier. In this case, the novel crystalline salts of epalrestat and/ornovel betaine cocrystal of epalrestat according to various embodimentsof the invention may represent intermediate forms of epalrestat used inthe preparation of the non-solid formulation. The novel crystallinesalts of epalrestat and novel betaine cocrystal of epalrestat accordingto various embodiments of the invention may provide advantages ofhandling stability and/or purity to the process of making suchformulations.

The invention also relates to the treatment and/or prevention ofdiabetes-associated disorders such as those discussed above. Theinvention provides methods for treating and/or preventingdiabetes-associated disorders by administering to mammals epalrestatcomprising one or more of the novel crystalline salt forms of epalrestatand/or novel betaine cocrystal of epalrestat as described herein, or apharmaceutical composition containing the same, in an amount sufficientto treat and/or prevent a condition treatable and/or preventable byadministration of a composition of the invention. That amount is theamount sufficient to exhibit any detectable therapeutic and/orpreventative or ameliorative effect. The effect may include, forexample, treatment and/or prevention of the conditions listed herein.These novel crystalline salt forms of epalrestat and novel betainecocrystal of epalrestat and pharmaceutical compositions containing themmay, according to various embodiments of the invention, be administeredusing any amount, any form of pharmaceutical composition, and any routeof administration effective, e.g. for treatment, all of which are easilydetermined by those of skill in the art through routine experimentation.After formulation with an appropriate pharmaceutically acceptablecarrier in a desired dosage, as known by those of skill in the art, thepharmaceutical compositions can be administered to humans and othermammals by any known method, such as, for example, orally, rectally, ortopically (such as by powders or other solid form-based topicalformulations). In certain embodiments, the novel crystalline salt formsof epalrestat and novel betaine cocrystal of epalrestat according tovarious embodiments of the invention may be administered at dosagelevels ranging from about 0.001 mg/kg to about 50 mg/kg, from about 0.01mg/kg to about 25 mg/kg, or from about 0.1 mg/kg to about 10 mg/kg ofsubject body weight per day, one or more times a day, to obtain thedesired therapeutic effect. It will also be appreciated that dosagessmaller than about 0.001 mg/kg or greater than about 50 mg/kg (forexample, ranging from about 50 mg/kg to about 100 mg/kg) can also beadministered to a subject in certain embodiments of the invention. Asdiscussed above, the amount required for a particular patient willdepend upon a variety of factors including the disorder being treatedand/or prevented; its severity; the specific pharmaceutical compositionemployed; the age, body weight, general health, gender, and diet of thepatient; the mode of administration; the time of administration; theroute of administration; and the rate of excretion of epalrestat; theduration of the treatment; any drugs used in combination or coincidentalwith the specific compound employed; and other such factors well knownin the medical arts. And, as also discussed, the pharmaceuticalcomposition of the novel crystalline salts of epalrestat and/or novelbetaine cocrystal of epalrestat as described herein may be administeredas a unit dosage form.

Although the present invention herein has been described with referenceto various exemplary embodiments, it is to be understood that theseembodiments are merely illustrative of the principles and applicationsof the present invention. Those having skill in the art would recognizethat a variety of modifications to the exemplary embodiments may bemade, without departing from the scope of the invention.

Moreover, it should be understood that various features and/orcharacteristics of differing embodiments herein may be combined with oneanother. It is therefore to be understood that numerous modificationsmay be made to the illustrative embodiments and that other arrangementsmay be devised without departing from the scope of the invention.

Furthermore, other embodiments of the invention will be apparent tothose skilled in the art from consideration of the specification andpractice of the invention disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with a scopeand spirit being indicated by the claims.

EXAMPLES Example 1 Preparation of a Crystalline Potassium Anhydrate Saltof Epalrestat

A mixture of 2.78 grams (8.70 mmol) of epalrestat free acid, 150 mL ofabsolute ethanol, and a solution of 855 mg (8.71 mmol) of potassiumacetate in 25 mL of absolute ethanol was placed in a sonication bath forabout 1 minute and stirred for about 10 minutes. Undissolved solid wascollected by vacuum filtration and was dried in a vacuum oven at ambienttemperature overnight to give 2.80 g (7.83 mmol, 90% yield) of thecrystalline potassium anhydrate salt of epalrestat. Analytical data wereobtained on the final product: the XRPD pattern was as shown in FIG. 1,the DSC thermogram was as shown in FIG. 5, the ¹H-NMR spectrum was asshown in FIGS. 9A-9D, and the TGA profile was as shown in FIG. 13.

Example 2 Preparation of a Crystalline Sodium Anhydrate Salt ofEpalrestat

A solution of 211 mg (0.661 mmol) of epalrestat free acid in 11 mL ofacetone was treated with 2.64 mL of a solution of 126 mg of sodiumbicarbonate in 4 mL of water and 2 mL of acetone (55.4 mg, 0.659 mmol ofsodium bicarbonate). Precipitation occurred and the solid was collectedby filtration and allowed to dry in the air to give 216 mg (0.633 mmol,96% yield) of the crystalline sodium anhydrate salt of epalrestat.Analytical data were obtained on the final product: the XRPD pattern wasas shown in FIG. 2, the DSC thermogram was as shown in FIG. 6, the¹H-NMR spectrum was as shown in FIGS. 10A-10D, and the TGA profile wasas shown in FIG. 14.

Example 3 Preparation of a Crystalline Sodium Anhydrate Salt ofEpalrestat

A mixture of solution containing 3.08 g (9.64 mmol) of epalrestat freeacid, 50 mL of methanol, and 3.75 mL of a solution of 516 mg of sodiumhydroxide in 5 mL of water (387 mg, 9.68 mmol of sodium hydroxide) wasbriefly placed in an ultrasonic bath and stirred for 10 minutes.Undissolved solid was collected by vacuum filtration and dried in avacuum oven at ambient temperature overnight to give 3.10 g (9.08 mmol,94% yield) of the crystalline sodium anhydrate salt of epalrestat.Analytical data were obtained on the final product: the XRPD pattern wassubstantially as shown in FIG. 2, the DSC thermogram was substantiallyas shown in FIG. 6, the ¹H-NMR spectrum was substantially as shown inFIGS. 10A-10D, and the TGA profile was substantially as shown in FIG.14.

Example 4 Preparation of a Crystalline 1-(2-hydroxyethyl)-pyrrolidineAnhydrate Salt of Epalrestat

A solution of 216 mg (0.676 mmol) of epalrestat in 15 mL of acetone wastreated with 82.1 μL of 1-(2-hydroxyethyl)-pyrrolidine. Crystallizationoccurred after about 45 seconds and the resulting solid was collected byfiltration to give the crystalline 1-(2-hydroxyethyl)-pyrrolidineanhydrate salt of epalrestat. Analytical data were obtained on the finalproduct: the XRPD pattern was as shown in FIG. 3, the DSC thermogram wasas shown in FIG. 7, the ¹H-NMR spectrum was as shown in FIGS. 11A-11D,and the TGA profile was as shown in FIG. 15.

Example 5 Preparation of a Betaine Hydrogen Diacid Cocrystal ofEpalrestat

A mixture of 176 mg (0.551 mmol) of epalrestat free acid and 10 mL ofmethanol was treated with 2.8 mL of a solution of 91 mg of betaine in 4mL of methanol (64 mg, 0.546 mmol of betaine). The sample began to clear(dissolve) and then became hazy. Precipitation occurred and the solidwas collected by filtration and allowed to dry in the air to give 124.5mg (60% yield) of betaine hydrogen diepalrestat. The crystals obtainedwere birefringent, yellow, fine blades. Analytical data were obtained onthe final product: the XRPD pattern was as shown in FIG. 4, the DSCthermogram was as shown in FIG. 8, the ¹H-NMR spectrum was as shown inFIGS. 12A-12D, the TGA profile was as shown in FIG. 16, and the DVSprofile was substantially as shown in FIG. 17.

Example 6 Preparation of a Betaine Hydrogen Diacid Cocrystal ofEpalrestat

A mixture of 2.10 grams (6.56 mmol) of epalrestat free acid, 769 mg(6.56 mmol) of betaine, and 150 mL of methanol was stirred for 10minutes. Undissolved solid was collected by vacuum filtration at ambienttemperature and were dried overnight in a vacuum oven under reducedpressure to give 2.08 g (84% yield) of betaine hydrogen diepalrestat.The crystals obtained were fine blades, micaceous particles, andrhombohedrals, yellow-orange in color. Analytical data were obtained onthe final product: the XRPD pattern was substantially as shown in FIG.4, the DSC thermogram was substantially as shown in FIG. 8, the ¹H-NMRspectrum was substantially as shown in FIGS. 12A-12D, the TGA profilewas substantially as shown in FIG. 16, and the DVS profile was as shownin FIG. 17. Elemental analysis was as follows:

% C % H % N % S Betaine (experimental) 55.56 4.88 5.56 17.16 Betainetheoretical 55.68 4.81 5.57 16.99

Example 7 Preparation of a Betaine Hydrogen Diacid Cocrystal ofEpalrestat

A solution of 91 mg (0.29 mmol) of epalrestat free acid, 33 mg (0.28 mg)of betaine, 0.10 mL of water, and 3 mL of THF was left in a fume hooduntil the solvents had evaporated. The remaining solid was found to bebetaine hydrogen diepalrestat by XRPD analysis. An XRPD pattern obtainedon the final product was substantially as shown in FIG. 4.

Example 8 Preparation of a Betaine Hydrogen Diacid Cocrystal ofEpalrestat

A solution of 2.17 g of betaine in 100 mL of methanol was added to 1.48g of epalrestat and the resulting slurry was sonicated for 3 minutes.The yellow solids were collected by filtration, rinsed twice withmethanol, and dried under reduced pressure to give 1.46 g of betainehydrogen diepalrestat. The crystals obtained were yellow andbirefringent. Analytical data were obtained on the final product: theXRPD pattern was substantially as shown in FIG. 4 and the ¹H-NMRspectrum was substantially as shown in FIGS. 12A-12D. Solubility datawere obtained in water on the final product, and the solubility profileis shown in FIG. 18A. As can be seen in FIG. 18B, epalrestat dissolvesmore quickly in water from the betaine hydrogen diacid cocrystal than itdoes from the free acid.

What is claimed is:
 1. A crystalline potassium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid.
 2. The crystalline potassium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid of claim 1, having substantially the same XRPD pattern as in FIG.
 1. 3. A pharmaceutical composition comprising the crystalline potassium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim
 1. 4. A method of treating, preventing, and/or delaying development any of the following conditions, comprising administering a pharmaceutical composition comprising the crystalline potassium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim 1: cardiac tissue ischemia, diabetic neuropathy, diabetic nephropathy, diabetic cardiomyopathy, cardiac autonomic neuropathy, diabetic retinopathy, diabetic macular edema, diabetic gastroparesis, cataracts, foot ulcers, diabetic macroangiopathy, diabetic microangiopathy, and neurological or neurodegenerative disorders.
 5. A method of inhibiting aldose reductase in a mammal in need thereof, comprising administering a pharmaceutical composition comprising the crystalline potassium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim
 1. 6. A crystalline sodium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid.
 7. The crystalline sodium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid of claim 6, having substantially the same XRPD pattern as in FIG.
 2. 8. A pharmaceutical composition comprising the crystalline sodium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim
 6. 9. A method of treating, preventing, and/or delaying development any of the following conditions, comprising administering a pharmaceutical composition comprising the crystalline sodium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim 6: cardiac tissue ischemia, diabetic neuropathy, diabetic nephropathy, diabetic cardiomyopathy, cardiac autonomic neuropathy, diabetic retinopathy, diabetic macular edema, diabetic gastroparesis, cataracts, foot ulcers, diabetic macroangiopathy, diabetic microangiopathy, and neurological or neurodegenerative disorders.
 10. A method of inhibiting aldose reductase in a mammal in need thereof, comprising administering a pharmaceutical composition comprising the crystalline sodium anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim
 6. 11. A crystalline 1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid.
 12. The crystalline 1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid of claim 11, having substantially the same XRPD pattern as in FIG.
 3. 13. A pharmaceutical composition comprising the crystalline 1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim
 11. 14. A method of treating, preventing, and/or delaying development any of the following conditions, comprising administering a pharmaceutical composition comprising the crystalline 1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim 11: cardiac tissue ischemia, diabetic neuropathy, diabetic nephropathy, diabetic cardiomyopathy, cardiac autonomic neuropathy, diabetic retinopathy, diabetic macular edema, diabetic gastroparesis, cataracts, foot ulcers, diabetic macroangiopathy, diabetic microangiopathy, and neurological or neurodegenerative disorders.
 15. A method of inhibiting aldose reductase in a mammal in need thereof, comprising administering a pharmaceutical composition comprising the crystalline 1-(2-hydroxyethyl)-pyrrolidine anhydrate salt of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim
 11. 16. A betaine hydrogen diacid cocrystal of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid.
 17. The betaine hydrogen diacid cocrystal of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid of claim 16, having substantially the same XRPD pattern as in FIG.
 4. 18. A pharmaceutical composition comprising the betaine hydrogen diacid cocrystal of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim
 16. 19. A method of treating, preventing, and/or delaying development any of the following conditions, comprising administering a pharmaceutical composition comprising the betaine hydrogen diacid cocrystal of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim 16: cardiac tissue ischemia, diabetic neuropathy, diabetic nephropathy, diabetic cardiomyopathy, cardiac autonomic neuropathy, diabetic retinopathy, diabetic macular edema, diabetic gastroparesis, cataracts, foot ulcers, diabetic macroangiopathy, diabetic microangiopathy, and neurological or neurodegenerative disorders.
 20. A method of inhibiting aldose reductase in a mammal in need thereof, comprising administering a pharmaceutical composition comprising the betaine hydrogen diacid cocrystal of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim
 16. 21. A method of treating and/or preventing homocystinuria, and/or reducing levels of homocysteine in blood serum, in a mammal in need thereof, comprising administering a pharmaceutical composition comprising the betaine hydrogen diacid cocrystal of 5-[(1Z,2E)-2-methyl-3-phenylpropenylidene]-4-oxo-2-thioxo-3-thiazolidineacetic acid according to claim
 16. 